Originally posted by 69Boss302:
Originally posted by Rara:


Drilled rotors WILL crack on a street car, especially where the rotor is the same as was originally sized for the car from the factory.





Is there a rough timeline as to when I expect mine to crack? After ~2,500 miles, they are no worse for the wear.



They will crack when heated and cooled rapidly. HEre's a fun test, but obviosuly at your own discretion and caution:

Drive to 80mph, brake hard to a near stop without locking up brakes.
Repeat 3-5 times.

Then drive and cool for a mile.

Drive to 60mph, brake hard to a near stop without locking up brakes.
Repeat 3-5 times.

Then drive and cool.

Drive and brake from like 50 to 25 or something, medium pressure breaking, and go home.

If your rotors survive that, and you have to be legit about it, then obviously you should be ok. For awhile. Bedding your rotors in is the BEST test to see if they can take it. The reason we're all concerned here is that stock cross drilled rotors are usually made from thicker than stock rotors, they are precisely drilled, and the rotors have NEVER been used.

Used rotors have already heated and cooled, effectively they've been bed in with the pad. If you go and drill it up, obviously some of the metal will weaken since the rotors aren't forged, they are cast, and like the discussion ensuing down below in the 3L forum about cast vs. forged pistons, the van der waals forces or whatever that hold the cast metal together will be altered when drilling on used rotors.

For reference, my Baer rotors are 13" and are 1.25" thick, significantly larger and wider than stock ones. They are cross drilled (a mistake I won't make again), but the rotors are a large enough heat sink to take track abuse and not crack.

my .02
Suneil

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